Power take-off shaft system and agricultural vehicle

ABSTRACT

A power take-off shaft system for an agricultural vehicle includes an output shaft with a socket for a power take-off shaft stub located at one end of the output shaft, wherein the power take-off shaft stub is arranged in the socket. A control valve is arranged in the output shaft and includes a valve bore extending axially from the socket into the output shaft. A first piston is adjustably arranged inside the valve bore in the output shaft, and a shifting element is adjustably controlled by the first piston. A first gearwheel and a second gearwheel are disposed in engagement with the output shaft via the shifting element such that the first piston is adjustable between a first position and a second position. The control valve includes a second piston arranged on the first piston, where the first piston is adjustable into a neutral position by the second piston.

RELATED APPLICATIONS

This application claims priority to German Patent Application Ser. No.102019215041.1, filed Sep. 30, 2019, and German Patent Application Ser.No. 102019215057.8, filed Sep. 30, 2019, the disclosures of which arehereby incorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to an agricultural vehicle, and inparticular to a power take-off shaft system of an agricultural vehicle.

BACKGROUND

Generally, power take-off shaft systems are provided at the front orrear end of agricultural vehicles such as traction vehicles, tractors ortowing vehicles. In particular, the power take-off shaft systemscomprise a drivable output shaft and a power take-off shaft stub, adevice drive shaft being able to be fastened thereto and a working toolor an attachment being able to derive a torque therefrom. Typicalworking tools which require a drive, are balers, circular harrows andsprayers.

Conventional power take-off shaft systems, in particular multi-stagepower take-off shaft systems, may provide different speeds or permit ashifting of the operating modes of the power take-off shaft systems inthe load-free state. Modern power take-off shaft systems may havebetween 1 to 4 gears. Moreover, the use of power take-off shaft stubswith toothings having 6, 21, 20 or 22 teeth is carried out in accordancewith ISO 500, in which the power take-off shaft stubs are categorizedaccording to a type 1-4. A different geometry has to be provideddepending on the transmitted power. In particular, agricultural vehiclesmay be provided with power take-off shaft systems which have two gears,namely a first gear with an output speed of 540 r/min and a second gearwith an output speed of 1000 r/min at the rated engine speed of thetractor. A power take-off shaft stub which is operated at 540 r/min inthis case may have a toothing with 6 teeth and a power take-off shaftstub which is operated at 1000 r/min may have a toothing with 20 or 21teeth. The variable design of the power take-off shaft stub for thedifferent operating speeds may serve to protect against the inadvertentattachment of a device designed for 540 r/min to a vehicle which isdesigned for 1000 r/min.

In spite of this difference in the design of the power take-off shaftsystem, in particular the power take-off shaft stub, the operator isstill advised to activate the correct output speed for the working tool,whereby a risk is present of incorrectly selecting the transmissionratio and the resulting damage to the power take-off shaft system or theworking tool. The power take-off shaft system may be actuatable by anelectric switch or software. Moreover, sensors are additionally providedon the power take-off shaft system in order to identify which end of thepower take-off shaft stub or which power take-off shaft stub is arrangedon the power take-off shaft system. A further possibility is tomechanically block the first or second gear if the operator attempts toactivate the incorrect output speed for the attached working tool. EP 2922 721 A1 discloses such a power take-off shaft system.

The problems of the conventional power take-off shaft systems orvehicles are that they require too much constructional space and arecost-intensive. Moreover, the power take-off shaft systems arestructurally complex since, in particular, these systems require sensorsfor identifying the power take-off shaft stub. As a result, the powertake-off shaft systems are susceptible to repair and have a high levelof wear.

Thus, there is a need for a power take-off shaft system and anagricultural vehicle which substantially avoid the drawbacks known fromthe prior art and are of structurally simple design or have a reducedsusceptibility to repair or a lower level of wear.

SUMMARY

In the present disclosure, a power take-off shaft system for anagricultural vehicle is proposed. The power take-off shaft systemincludes an output shaft with a socket for a power take-off shaft stubwhich is provided at one end of the output shaft, where the powertake-off shaft stub is able to be arranged at least partially, and insome embodiments entirely, in the socket. Thus, the power take-off shaftsystem may comprise the power take-off shaft stub. The output shaftcomprises a control valve which is arranged, i.e., integrated, in theoutput shaft. The output shaft, in particular the control valve,comprises a valve bore which extends axially from the socket, inparticular from a base of the socket, into the output shaft. The outputshaft, in particular the control valve, further comprises a first pistonwhich is arranged so as to be adjustable, i.e., movable or displaceableor settable, inside the valve bore in the output shaft. The powertake-off shaft system, including the output shaft, further comprises ashifting element which is adjustable, e.g., also settable or movable ordisplaceable, by the first piston.

The power take-off shaft system further comprises a first gearwheel anda second gearwheel which are able to be brought into engagement, e.g.,fixedly in terms of rotation, with the output shaft by the shiftingelement. The first piston in this case is adjustable, i.e., movable ordisplaceable or even settable, in particular in an axial direction ofthe output shaft, between a first position in which the first pistonadjusts the shifting element such that the first gearwheel is engagedwith the shifting element and a second position in which the firstpiston adjusts the shifting element such that the second gearwheel isengaged with the shifting element. The output shaft, in particular thecontrol valve, has a second piston which is arranged so as to beadjustable, e.g., movable, displaceable or settable so as to be axiallymovable or displaceable, at least partially on, the first piston, forexample, inside a piston bore in the first piston. The second piston mayalso be arranged so as to be adjustable, i.e., arranged so as to beaxially movable or displaceable, inside the valve bore in the outputshaft. The first piston and thus in particular also the shifting elementis adjustable into the neutral position by the second piston.

The power take-off shaft system may be a multi-stage power take-offshaft system. The power take-off shaft system or the multi-stage powertake-off shaft system may be for an agricultural vehicle such as atraction vehicle or a tractor, towing vehicle or the like. Generally,the power take-off shaft system may be arranged on the agriculturalvehicle such as at the front, the rear or centrally. The power take-offshaft system may comprise a power take-off shaft controller or an inputshaft. The power take-off shaft system may comprise a first and a secondgearwheel pair. The first gearwheel pair may comprise the firstgearwheel and a third gearwheel. The second gearwheel pair may comprisethe second gearwheel and a fourth gearwheel. The third or fourthgearwheel may be connected in this case fixedly in terms of rotation tothe input shaft. Similarly, however, the power take-off shaft system mayalso comprise three or four or more gearwheel pairs, wherein at leastone gearwheel per gearwheel pair is shiftable. Each gearwheel pair maycomprise at least one gearwheel which is connected to the input shaftand comprise a further gearwheel which is able to be connected fixedlyin terms of rotation to the output shaft by the shifting element.

The input shaft may be arranged with the output shaft between an engineoutput and the power take-off shaft stub. The input shaft may beoperatively connected to the output shaft by a gearwheel pair. Inparticular, the input shaft may be operatively coupled or may becouplable to the output shaft by the first or second gearwheel pair.

The shifting element may be arranged on the outer surface of the outputshaft. The shifting element may be engaged, e.g., engaged fixedly interms of rotation, with the output shaft. The shifting element may beconnected or coupled to the first piston such as part of the firstpiston or fastened to the first piston. The shifting element permits agearwheel, i.e., the first or second gearwheel, to be connected fixedlyin terms of rotation to the output shaft, i.e., to operate the powertake-off shaft system with at least two gears. In this case, the firstposition may correspond to the first gear and the second position maycorrespond to the second gear. With an arrangement which operates twogearwheels with one shifting element, a compact design may beimplemented. Two or more shifting elements may also be provided, i.e.,the output shaft may have a first and a second shifting element by whichthe first and second gearwheel are individually shiftable. Inparticular, however, the input shaft may also have a third shiftingelement.

In the neutral position, the shifting element is not able to be engagedwith a gearwheel, in particular neither with the first nor the secondgearwheel. Thus the shifting element may be configured or arranged suchthat it permits the gearwheels to be connected fixedly in terms ofrotation to the output shaft or to operate this in the neutral positionin freewheel mode. Thus the first piston may be displaceable in theaxial direction of the output shaft between the first position or thesecond position or the neutral position so that the shifting element isalso adjustable in the axial direction of the output shaft. If the firstpiston is in the first position in which the first piston adjusts theshifting element such that the first gearwheel is engaged with theshifting element, the power take-off shaft system may be operated in thefirst gear at the lower speed, e.g., 540 r/min. If the piston is in thesecond position in which the first piston adjusts the shifting elementsuch that the second gearwheel is engaged with the shifting element, thepower take-off shaft system may be operated in the second gear at thehigher speed, e.g., 1000 r/min. The first piston, however, may also beadjustable between a third or fourth position or a plurality ofpositions. In the third position the first piston may adjust theshifting element such that a third gearwheel is engaged with theshifting element. In the fourth position, the first piston may adjustthe shifting element such that a fourth gearwheel is engaged with theshifting element.

The two-part construction of the piston, which permits a reduction inthe constructional space for the output shaft, is essential to thepresent disclosure, as additional coupling elements and shiftingelements for coupling the gearwheels and for shifting into the neutralposition can be dispensed with. Moreover, the power take-off shaftsystem is of structurally simpler design so that, for example, thesusceptibility to repair or the wear of the power take-off shaft systemcan be reduced.

In one embodiment of the present disclosure, the second piston isadjustable inside the piston bore by the power take-off shaft stubdepending on an alignment of the power take-off shaft stub in thesocket, such that a movement of the first piston into the secondposition is blocked by the second piston, i.e., in particular anadjustment of the shifting element is also at least partially prevented.In other words, the first piston may be blocked by the second pistondepending on an alignment or arrangement of the power take-off shaftstub, in particular a first or second stub end, in the socket. Thus, bythe power take-off shaft stub the second piston may be adjustablebetween a first position in which the second piston at least partiallyprotrudes into the socket and the second piston is able to be receivedat least partially in a recess of the power take-off shaft stub, and asecond position in which the power take-off shaft stub adjusts thesecond piston such that this second piston blocks the first piston sothat a movement of the first piston into the second position isprevented.

In particular, the power take-off shaft stub may have a first stub endwith a first profile, in particular a recess, and a first toothing or asecond stub end with a second profile and a second toothing. The powertake-off shaft stub may thus be a short shaft with one or two or moretoothings, one for the drive and one for the output. In the case of areversible power take-off shaft stub, a third toothing may be providedfor adapting to different splined articulated shafts. Instead of areversible power take-off shaft stub, two or more power take-off shaftstubs may also be interchanged. The power take-off shaft stub with thefirst stub end may be arranged in the socket, wherein the recess at thefirst stub end is able to receive the second piston which protrudes atleast partially into the socket. In this case, the first piston may beadjustable into the first and the second position. However, the powertake-off shaft stub may also be arranged with the second stub end in thesocket, wherein the second piston protruding into the socket is adjustedfrom the second stub end in the direction of the first piston. In thiscase, the first piston may be adjusted only into the first position andan adjustment of the first piston into the second position is blockableor is blocked by the second piston.

In principle, however, two power take-off shaft stubs may be provided,in each case with a profile and a toothing on one respective first stubend. The socket may also comprise a releasable closure mechanism forsecuring the power take-off shaft stub. A mechanism for blocking thesecond position of the first piston, i.e., of the gear at the higherspeed, may thus advantageously be provided. The engagement of the powertake-off shaft stub at a higher speed may be automatically preventedthereby, depending on an alignment of the power take-off shaft stub inthe socket or the type of power take-off shaft stub. Moreover, thereliability of the power take-off shaft system is improved and the useof sensors avoided. This represents an improvement in the safety of thepower take-off shaft system and requires the power take-off shaft stubto be arranged in the correct orientation or the correct type of powertake-off shaft stub to be arranged in the socket before a correspondingspeed may be activated.

In one embodiment of the present disclosure, the second piston comprisesa first piston element and a second piston element and a third pistonelement, wherein the first piston element is arranged so as to beadjustable at least partially in the first piston, the second pistonelement is arranged so as to be adjustable at least partially in thefirst piston element and the third piston element is arranged so as tobe adjustable at least partially in the second piston element. Thefirst, second and third piston element may be arranged so as to beadjustable, e.g., arranged so as to be movable or displaceable orsettable, and arranged so as to be axially movable or displaceable. Thefirst piston element may be arranged, for example, so as to beadjustable inside the piston bore in the first piston. Moreover, thefirst piston element may also be arranged so as to be adjustable, i.e.,arranged so as to be movable or displaceable or settable, and arrangedso as to be axially movable or displaceable inside the valve bore in theoutput shaft. The second piston element may be arranged, for example, soas to be adjustable inside a further piston bore in the first pistonelement. Moreover, the second piston element may also be arranged so asto be adjustable and arranged so as to be axially movable ordisplaceable inside the valve bore in the output shaft. The third pistonelement may be arranged so as to be adjustable at least partially insidea third piston bore in the second piston element. Moreover, the thirdpiston element may protrude at least partially into the socket or thefurther piston bore or may be also arranged so as to be adjustable,i.e., arranged so as to be movable or displaceable or settable, andarranged so as to be axially movable or displaceable inside the valvebore in the output shaft. The third piston element may be connected tothe first piston, in particular coupled to the first piston or fastenedthereto. The third piston element may be adjustable by the powertake-off shaft stub depending on an alignment of the power take-offshaft stub in the socket, such that a movement of the first piston intothe second position is blocked by the first and second and third pistonelement, i.e., in particular an adjustment of the shifting element isalso prevented. This measure permits greater damping of the mechanism sothat the susceptibility to repair or the wear is reduced.

In one embodiment of the present disclosure, the second piston elementis mounted in the first piston element by a first restoring element, inparticular mounted in a balanced position, or the third piston elementcomprises a first and second piston part which are arranged so as to beadjustable in the second piston element, wherein a second restoringelement is arranged between the first and second piston part, inparticular the first and second piston part are mounted by the secondrestoring element in a balanced position. The first or second restoringelement may be a resilient element, such as a spring element or aspring. The first or the second restoring element may be in a balancedor resting position in the neutral position. The first restoring elementis able to pretension the first or second piston element such that thefirst piston is adjustable back into the neutral position by the firstrestoring element. The first piston may be adjustable, in particular bythe first restoring element, from the first and second position backinto the neutral position.

The second restoring element is able to pretension the third pistonelement such that the first piston is adjustable back into the neutralposition by the second restoring element. When the first piston isadjusted into the first or second position, the third piston element maybe pretensioned by the second restoring element in the second pistonelement. The first and second piston part may be connected together bythe second restoring element or coupled by the second restoring element,in particular the second restoring element may be fastened at leastpartially to the first and second piston part. The second restoringelement and the first and second piston part may be arranged along anaxis of the output shaft, in particular coaxially along the axis of theoutput shaft. The first piston part may be connected to the firstpiston, i.e., coupled to the first piston or fastened thereto. Thesecond piston part may protrude into the socket.

The first piston part may be adjustable by the power take-off shaft stubdepending on an alignment of the power take-off shaft stub in the socketsuch that the second restoring element pretensions the first and secondpiston part and a movement of the first piston into the second positionis blocked by the first and second piston element and the first andsecond piston part, i.e., in particular an adjustment of the shiftingelement is also prevented. The first and second restoring element permita greater damping of the power take-off shaft system and an automaticmechanical controllability.

In one embodiment of the present disclosure, a first fluid conveyancebore is provided in the output shaft at least partially in the outputshaft and at least partially in the first piston. A pressurized fluid,such as hydraulic fluid, is able to be conveyed thereby into the outputshaft (i.e., via the valve bore) such that the first piston is movedinto the first position or a second fluid conveyance bore is provided inthe output shaft, the pressurized fluid being able to be conveyedthereby into the output shaft such that the first piston is moved intothe second position. The control valve may comprise the first and secondfluid conveyance bore. The first fluid conveyance bore may be in twoparts. The first fluid conveyance bore may thus be configured at leastpartially in the output shaft and at least partially in the firstpiston. In this case, the part of the first fluid conveyance bore whichis configured in the piston may be arranged at least partially in thepart of the first fluid conveyance bore which is configured in theoutput shaft. The part of the first fluid conveyance bore which isarranged in the output shaft, therefore, may have a different diameter(e.g., a greater diameter) than the part of the first fluid conveyancebore which is arranged in the first piston. The pressurized fluid may beguided in the first fluid conveyance bore via the output shaft into thefirst piston in the piston bore such that the first piston is moved intothe first position. The piston bore may in this case be configured atleast partially, but also entirely, as the first chamber and filled withthe pressurized fluid so that the first piston is moved into the firstposition. The pressurized fluid may be guided in the second fluidconveyance bore via the output shaft between the first piston and thebase of the valve bore so that the first piston is moved into the secondposition.

The volume between the first piston and the base of the valve bore maybe configured in this case at least partially, but also entirely, as thesecond chamber and filled with the pressurized fluid so that the firstpiston is moved into the second position. The power take-off shaftsystem or the agricultural vehicle may also comprise a mechanism, forexample, hoses or tubes or lines or a pump, for supplying the fluid tothe respective conveyance bore. The first or second position may thus beactivated by the pressurized fluid, which is able to be conveyed throughthe first or second fluid conveyance bore in the output shaft.Advantageously, this permits a structurally simpler design of the powertake-off shaft system, since mechanical connections in the form ofshifting rods, shift forks, gear shift linkages are dispensed with inthe gear unit. By the provision of the first and second fluid conveyancebore in the output shaft the mechanism for selecting the first andsecond gearwheel may be controlled in a simple manner, in particularhydraulically. Due to the structurally optimized design, the powertake-off shaft system has a longer service life and is easier tooperate.

In one embodiment of the present disclosure, the power take-off shaftstub has a first and second stub end. The first and second stub end areable to be arranged at least partially, in particular entirely, in thesocket and the first stub end comprises a toothing which is differentfrom the second stub end. The first stub end may have a first toothingwith 6, 21, 22, or 22 teeth or a cylindrical shape without teeth. Thesecond stub end may have a second toothing with 6, 21, 22 or 22 teeth ora cylindrical shape without teeth. The toothing with 6 teeth may have asplined shaft profile with a 35 mm diameter. The toothing with 20 or 21teeth may have a splined shaft profile with a 35 mm diameter and thetoothing with 21 teeth may have a splined shaft profile with a 45 mmdiameter. Moreover, a toothing with 22 teeth which has a splined shaftprofile with a 57.5 mm diameter may be used. Advantageously, it ispossible to identify which stub end is arranged in the socket, accordingto the arrangement of the respective toothing in the socket.

In one embodiment of the present disclosure, the first stub end, inparticular a base of the first stub end, has a first profile with arecess and the second stub end, in particular a base of the second stubend, has a second profile which is planar, i.e., it has no recess. Thefirst profile of the first stub end may at least partially, inparticular entirely, receive the protruding second piston part, i.e.,due to the recess, when this second piston part is arranged in therecess. As a result, the first piston is not blocked and thus may beadjusted into the first and second position. The second stub end withthe second profile may adjust the second piston part, in particulardisplace the second piston part, in the direction of the first pistonpart such that by the first piston part a movement of the first pistonis blockable, in particular an adjustment of the shifting element intothe second position is prevented. In particular, when the first stubend, which has a recess and the first toothing in particular with 6teeth, is arranged in the socket, therefore, the first piston isadjustable into the first and second position so that an activation ofthe lower speed (540 or 1000 revolutions per minute) and the higherspeed (1000 or 1300 revolutions per minute) is possible. In particular,when the second stub end which has no recess and the second toothing, inparticular with 21 teeth or a cylindrical shape, is arranged in thesocket, the first piston may be adjustable only into the first positionso that only an activation of the lower speed is possible and noactivation of the higher speed is possible. This advantageously makes itpossible to create a power take-off shaft system which is structurallyless susceptible to repair and wear.

The present disclosure further relates to an agricultural vehicle havinga power take-off shaft system. The agricultural vehicle may be atraction vehicle, tractor or towing vehicle. The power take-off shaftsystem may be arranged on the vehicle at the front or in the center orat the rear in the direction of travel of the vehicle. In specificembodiments, the agricultural vehicle may comprise a power take-offshaft system in order to provide power to a working tool via anarticulated shaft. The agricultural vehicle according to the presentdisclosure has the above-described advantages of the power take-offshaft system.

The power take-off shaft system or the agricultural vehicle may have acontrol device, in particular two or more control devices, which may beoperated to control, regulate, or adjust (e.g., set or alter) the powertake-off shaft system or the agricultural vehicle, in particular thecontrol valve, such that the first piston is adjustable between thefirst and second position and the neutral position. Moreover, the powertake-off shaft system or the agricultural vehicle may be controllable orregulatable by the control unit. The control unit (ECU refers toelectronic control unit or ECM refers to electronic control module) maybe an electronic module or an embedded system. The control unit may beprovided on the power take-off shaft system or the agricultural vehicle.The control unit may also be allocated between the power take-off shaftsystem and the agricultural vehicle. The control unit and the powertake-off shaft system or the agricultural vehicle, in particular a firstor second valve for controlling or regulating the supply of fluid intothe first and second fluid conveyance bore, may be connected together bya cable or wire, or even wirelessly, i.e., by radio.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned aspects of the present disclosure and the manner ofobtaining them will become more apparent and the disclosure itself willbe better understood by reference to the following description of theembodiments of the disclosure, taken in conjunction with theaccompanying drawing, wherein:

FIG. 1 shows a schematic side view of a first exemplary embodiment of anagricultural vehicle according to the present disclosure,

FIG. 2 shows a schematic view of a power take-off shaft system accordingto the present disclosure with a first piston in a neutral position,

FIG. 3 shows a schematic view of a power take-off shaft system accordingto the present disclosure with the piston in the first position,

FIG. 4 shows a schematic plan view of the power take-off shaft systemwith the first piston in the second position, and

FIG. 5 shows a schematic plan view of the power take-off shaft systemwith the first piston in the neutral position and a blocked secondposition.

Corresponding reference numerals are used to indicate correspondingparts in the drawings.

DETAILED DESCRIPTION

The embodiments of the present disclosure described below are notintended to be exhaustive or to limit the disclosure to the preciseforms disclosed in the following detailed description. Rather, theembodiments are chosen and described so that others skilled in the artmay appreciate and understand the principles and practices of thepresent disclosure.

FIG. 1 shows a schematic side view of a first embodiment of anagricultural vehicle 10 according to the present disclosure which isable to move in a forward direction of travel 18. The vehicle 10, shownschematically in FIG. 1, comprises a power take-off shaft system 12according to the present disclosure. The power take-off shaft system 12may be used in order to permit a supply of driving power to a workingtool. On such a vehicle 10, the power take-off shaft system 12 isgenerally provided on the vehicle 10 at the front, in the center or atthe rear in the forward direction of travel. As shown in FIG. 1, it isprovided at the rear.

A working tool may be coupled and attached to the vehicle 10 and thepower take-off shaft system 12. Conventional speeds of the powertake-off shaft system 12 may be 540 or 1000 or 1300 revolutions perminute. It is also possible to operate the power take-off shaft system12 at the cited speeds in a reduced power mode. The agricultural vehicle10 may have a control device 16 or a display device 14. The controldevice 16, however, may also be configured as a part of the powertake-off shaft system 12.

FIG. 2 shows a schematic view of a power take-off shaft system 12according to the present disclosure, in particular parts of the powertake-off shaft system 12, with a first piston 110 in a neutral position.The power take-off shaft system 12 shown in FIG. 2 correspondssubstantially to the power take-off shaft system 12 shown in FIG. 1 sothat hereinafter only the differences are described. The power take-offshaft system 12 comprises an output shaft 100 with a socket 102 for apower take-off shaft stub 104 provided at one end of the output shaft,wherein the power take-off shaft stub 104 is able to be arranged atleast partially in the socket 102. Moreover, the output shaft 100comprises a control valve 106 which is arranged in the output shaft 100.The output shaft 100, in particular the control valve 106, comprises avalve bore 108 which extends axially from the socket 106 into the outputshaft 100 and comprises a first piston 110 which is adjustably arrangedinside the valve bore 108 in the output shaft 100. Moreover, a shiftingelement 112 which is adjustable by the first piston 110 is provided. Theshifting element 112 is also connected to the first piston 110 and isengaged fixedly in terms of rotation with the output shaft 100.

The power take-off shaft system 12 further comprises a first gearwheel114 and a second gearwheel 116 which are able to be brought intoengagement, in particular are able to brought into engagement fixedly interms of rotation, with the output shaft 100 by the shifting element112. The first piston 110 is adjustable between a first position inwhich the first piston 110 adjusts the shifting element 112 such thatthe first gearwheel 114 is engaged with the shifting element 112, and asecond position in which the first piston 110 adjusts the shiftingelement 112 such that the second gearwheel 116 is engaged with theshifting element 112. The output shaft 100, in particular the controlvalve 106, has a second piston 118 which is arranged so as to beadjustable (i.e., displaceable) at least partially on the first piston110, wherein the second piston 118 is arranged so as to be adjustable(i.e., displaceable) at least partially in the first piston 110 inside apiston bore (reference numeral 126 see FIG. 3). The first piston 110 isadjustable (i.e., displaceable) into a neutral position by the secondpiston 118. The second piston 118 may moreover be adjustable by thepower take-off shaft stub 104 such that a movement of the first piston110 into the second position is blockable by the second piston 118.

As shown in FIG. 2, the first piston 110 is also adjustable, e.g.,movable or displaceable, into a neutral position in which the shiftingelement 112 is engaged neither with the first nor with the secondgearwheel 114, 116.

If the shifting element 112 is engaged with the first or secondgearwheel 114, 116, it connects these gearwheels fixedly in terms ofrotation to the output shaft 100. If the first piston 110 is in thefirst position the power take-off shaft system may be operated at onespeed, in particular the lower speed. If the first piston 110 is in thesecond position, the power take-off shaft system 12 may be operated at adifferent speed (i.e., at the higher speed). The second piston 118comprises a first piston element 120, a second piston element 122 and athird piston element 124. The first piston element 120 is adjustablyarranged at least partially in the first piston 110 inside the pistonbore (reference numeral 126, see FIG. 3). The second piston element 122is adjustably arranged at least partially in the first piston element120 inside a further piston bore 128. Moreover, the second pistonelement 122 is mounted in the first piston element 120 by a firstrestoring element 132.

The third piston element 124 is adjustably arranged at least partiallyin the second piston element 122 inside a third piston bore 130. Thethird piston element 124 comprises a first and second piston part 124.1,124.2 which are adjustably arranged in the second piston element 122inside the third piston bore 130, wherein a second restoring element 134is arranged between the first and second piston part 124.1, 124.2. Thefirst piston part 124.1 is coupled to the first piston 110 and thesecond piston part 124.2 protrudes into the socket 102. The first andsecond restoring element 132, 134 are configured as a resilient element,in this case a spring. If the first piston 110 is located in the neutralposition, the first or second restoring element 132, 134 may be in abalanced or resting position.

Moreover, a first fluid conveyance bore 140 is provided at leastpartially in the output shaft 100 and at least partially in the firstpiston 110, a pressurized fluid being able to be conveyed thereby intothe output shaft 100 such that the first piston 110 is moved into thefirst position. The first fluid conveyance bore is thus configured intwo parts, wherein the part of the first fluid conveyance bore 140.2which is configured in the piston 110 is arranged at least partially inthe part of the first fluid conveyance bore 140.1 which is configured inthe output shaft 100. Moreover, a second fluid conveyance bore 142 isconfigured in the output shaft 100, the pressurized fluid being able tobe conveyed thereby into the output shaft 100 such that the first piston110 is moved into the second position.

The power take-off shaft stub 104 has a first stub end 150 and a secondstub end (reference numeral 152, see FIG. 5) which may be at leastpartially arranged in the socket. The first stub end 150 has a toothingwhich is different from the second stub end 152. The first stub end 150may, for example, have a first toothing with 6 teeth and the second stubend 152 may have a second toothing with 21 teeth. Moreover, the firststub end 150 comprises a first profile with a recess 154 and the secondstub end 152 comprises a second profile which is planar (see FIG. 5).

FIG. 3 shows a schematic view of a power take-off shaft system 12according to the present disclosure, in particular parts of the powertake-off shaft system 12 with the first piston 110 in the firstposition. The power take-off shaft system 12 shown in FIG. 3substantially corresponds to the power take-off shaft system shown inFIGS. 1 and 2 so that only the differences are described hereinafter.The piston bore 126 is configured as a first chamber 160. If the firstchamber 160 is filled with the pressurized fluid, the first piston 110is moved into the first position. In this case, the first restoringelement 132 pretensions the second piston element 122 such that thefirst piston 110 is adjustable back into the neutral position by thefirst restoring element 132. Moreover, the second restoring element 134may additionally pretension the third piston element 124 such that thefirst piston 110 is also adjustable into the neutral position by thesecond restoring element 134. Moreover, the power take-off shaft stub104 with the first stub end 150 with the first profile and the firsttoothing is arranged in the socket 102, wherein the recess 154 on thefirst stub end 150 receives the second piston part 124.2 which protrudesinto the socket 102.

FIG. 4 shows a schematic plan view of the power take-off shaft system12, in particular parts of the power take-off shaft system 12 with thefirst piston 110 in the second position. The power take-off shaft system12 shown in FIG. 4 corresponds substantially to the power take-off shaftsystem 12 shown in FIGS. 1 to 3, so that only the differences aredescribed hereinafter. The pressurized fluid may be guided in the secondfluid conveyance bore 142 via the output shaft 100 into the volume whichis located between the first piston 110 and the base of the valve bore108 and which is configured as the second chamber 162. If the secondchamber 162 is filled with the pressurized fluid, the first piston 110is moved into the second position. In this case the first restoringelement 132 pretensions the first and second piston element 120, 122,but in particular the first piston element 120, such that the firstpiston 110 is adjustable back into the neutral position by the firstpiston element 120 which is pretensioned by the first restoring element132. Moreover, the second restoring element 134 may additionallypretension the third piston element 124 such that the first piston 110is also adjustable back into the neutral position by the secondrestoring element 134.

FIG. 5 shows a schematic plan view of the power take-off shaft system12, in particular parts of the power take-off shaft system 12, with thefirst piston 110 in the neutral position and a blocked second position.The power take-off shaft system 12 shown in FIG. 5 substantiallycorresponds to the power take-off shaft system 12 shown in FIGS. 1 to 4,so that only the differences are described hereinafter. The essentialdifference from the power take-off shaft systems 12 shown in FIGS. 1 to4 is that the power take-off shaft stub 104 with the second stub end 152with the second profile and the second toothing is arranged in thesocket 102, wherein the second piston part 124.2 protruding into thesocket 102 is adjusted by the second stub end 152 in the direction ofthe first piston part and along an axis of the third piston element 124.

In this case, the second restoring element 134 pretensions the thirdpiston element 124, i.e., thus the second piston 118 and the componentsthereof as a whole, such that an adjustment of the first piston 110 intothe second position is blockable or is blocked by the second piston 118.

While embodiments incorporating the principles of the present disclosurehave been disclosed hereinabove, the present disclosure is not limitedto the disclosed embodiments. Instead, this application is intended tocover any variations, uses, or adaptations of the disclosure using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this disclosure pertains and which fallwithin the limits of the appended claims.

1. A power take-off shaft system for an agricultural vehicle,comprising: an output shaft with a socket for a power take-off shaftstub located at one end of the output shaft, wherein the power take-offshaft stub is arranged at least partially in the socket, a control valvearranged in the output shaft and including a valve bore extendingaxially from the socket into the output shaft; a first piston adjustablyarranged inside the valve bore in the output shaft; a shifting elementadjustably controlled by the first piston; a first gearwheel and asecond gearwheel disposed in engagement with the output shaft via theshifting element; wherein the first piston is adjustable between a firstposition and a second position; wherein, in the first position, thefirst piston adjusts the shifting element such that the first gearwheelis engaged with the shifting element; wherein, in the second position,the first piston adjusts the shifting element such that the secondgearwheel is engaged with the shifting element; wherein, the controlvalve comprises a second piston adjustably arranged at least partiallyon the first piston, where the first piston is adjustable into a neutralposition by the second piston.
 2. The power take-off shaft system ofclaim 1, wherein the second piston is adjustable by the power take-offshaft stub such that a movement of the first piston into the secondposition is blocked by the second piston.
 3. The power take-off shaftsystem of claim 1, wherein the second piston comprises a first pistonelement, a second piston element, and a third piston element.
 4. Thepower take-off shaft system of claim 3, wherein: the first pistonelement is adjustably arranged at least partially in the first piston;the second piston element is adjustably arranged at least partially inthe first piston element; and the third piston element is adjustablyarranged at least partially in the second piston element.
 5. The powertake-off shaft system of claim 3, wherein the second piston element ismounted in the first piston element by a first restoring element.
 6. Thepower take-off shaft system of claim 3, wherein the third piston elementcomprises a first and second piston part adjustably arranged in thesecond piston element.
 7. The power take-off shaft system of claim 6,wherein a second restoring element is arranged between the first andsecond piston part.
 8. The power take-off shaft system of claim 1,further comprising a first fluid conveyance bore defined in the outputshaft.
 9. The power take-off shaft system of claim 8, wherein apressurized fluid is conveyed through the first fluid conveyance boreinto the output shaft such that the first piston is moved into the firstposition.
 10. The power take off shaft system of claim 9, furthercomprising a second fluid conveyance bore in the output shaft, whereinthe pressurized fluid is conveyed through the second fluid conveyancebore into the output shaft such that the first piston is moved into thesecond position.
 11. The power take-off shaft system of claim 1, whereinthe power take-off shaft stub comprises a first stub end and a secondstub end arranged at least partially in the socket.
 12. The powertake-off shaft system of claim 11, wherein the first stub end comprisesa toothing which is different from the second stub end.
 13. The powertake-off shaft system of claim 11, wherein the first stub end comprisesa first profile with a recess and the second stub end comprises a secondprofile which is planar.
 14. An agricultural vehicle, comprising: apower take-off shaft system coupled to the vehicle; a working toolcoupled to the power take-off shaft system; wherein, the power take-offshaft system comprises: an output shaft with a socket for a powertake-off shaft stub located at one end of the output shaft, wherein thepower take-off shaft stub is arranged at least partially in the socket,a control valve arranged in the output shaft and including a valve boreextending axially from the socket into the output shaft; a first pistonadjustably arranged inside the valve bore in the output shaft; ashifting element adjustably controlled by the first piston; a firstgearwheel and a second gearwheel disposed in engagement with the outputshaft via the shifting element; wherein the first piston is adjustablebetween a first position and a second position; wherein, in the firstposition, the first piston adjusts the shifting element such that thefirst gearwheel is engaged with the shifting element; wherein, in thesecond position, the first piston adjusts the shifting element such thatthe second gearwheel is engaged with the shifting element; wherein, thecontrol valve comprises a second piston adjustably arranged at leastpartially on the first piston, where the first piston is adjustable intoa neutral position by the second piston.
 15. The agricultural vehicle ofclaim 14, wherein the second piston is adjustable by the power take-offshaft stub such that a movement of the first piston into the secondposition is blocked by the second piston.
 16. The agricultural vehicleof claim 14, wherein: the second piston comprises a first pistonelement, a second piston element, and a third piston element; the firstpiston element is adjustably arranged at least partially in the firstpiston; the second piston element is adjustably arranged at leastpartially in the first piston element; and the third piston element isadjustably arranged at least partially in the second piston element. 17.The agricultural vehicle of claim 16, wherein the second piston elementis mounted in the first piston element by a first restoring element. 18.The agricultural vehicle of claim 16, wherein the third piston elementcomprises a first and second piston part adjustably arranged in thesecond piston element.
 19. The agricultural vehicle of claim 18, whereina second restoring element is arranged between the first and secondpiston part.
 20. A power take-off shaft system for an agriculturalvehicle, comprising: an output shaft with a socket for a power take-offshaft stub located at one end of the output shaft, wherein the powertake-off shaft stub comprises a first stub end and a second stub endarranged at least partially in the socket; a control valve arranged inthe output shaft and including a valve bore extending axially from thesocket into the output shaft; a first piston adjustably arranged insidethe valve bore in the output shaft, the first piston adjustably movablebetween a first position and a second position; a shifting elementadjustably controlled by the first piston; a first gearwheel and asecond gearwheel disposed in engagement with the output shaft via theshifting element; and a first fluid bore and a second fluid bore, wherepressurized fluid is configured to flow through the first fluid borewhen the first piston is moved into the first position and through thesecond fluid bore when the first piston is moved into the secondposition; wherein, in the first position, the first piston adjusts theshifting element such that the first gearwheel is engaged with theshifting element; wherein, in the second position, the first pistonadjusts the shifting element such that the second gearwheel is engagedwith the shifting element; wherein, the control valve comprises a secondpiston adjustably arranged at least partially on the first piston, wherethe first piston is adjustable into a neutral position by the secondpiston.